3-D model mimics volcanic blast

Simulation of the May 18, 1980, blast at Mount St. Helens at 380 seconds.

A new 3-D model that realistically mimics the 1980 eruption of Mount St. Helens is helping scientists understand the dynamics of such blasts and may help them map potential blast flows at dangerous volcanoes around the world.

The eruption of the volcano in Washington killed 57 people, leveled forests and sent a torrent of mud and debris down rivers that wiped out hundreds of homes and dozens of bridges.

The damage stems from a fast-moving current of superheated gas and hot rock and debris that was blasted out sideways from the volcano, Barry Voight, an emeritus professor of geology at Penn State, explained to me today.

For more than 30 years, he and other researchers have been trying to understand the physics behind the devastating nature of this blast. "It has always remained enigmatic and something that was hard to explain," he said.

Beginning about five years ago, the scientists harnessed state-of-the-art computers to create a 3-D model of the blast, including the mass, momentum and heat energy of the gas, as well as properties of the solid particles. They then compared the results of the model to what was observed in the field.

"The matchup is quite good," Voight said, noting that the topography around the volcano and the energy of the flow were the most important factors determining where the blast traveled. Such blasts, for example, are blocked by mountains and channeled down river ravines and canyons.

Now that the researchers have accurately modeled the Mount St. Helens blast from 1980, they can use the same technology to model blast flows at potentially dangerous volcanoes around the world. Already, it is being used to model the Montserrat volcano in the Caribbean.

"We can put in a couple of different [gas] pressures, for example, and see where the area of devastation is and then use that to influence zoning decisions," Voight said.

Findings appear in the June issue of Geology. Other researchers on the team are Tomaso Esposti Ongaro and Augusto Neri, Istituto Nazionale di Geofisica e Vulcanologia, Pisa, Italy; C. Widiwidjayanti, formerly at Penn State but now at Nanyang Technological University, Singapore; and Amanda B. Clarke, Arizona State University.